1. Technical Field
The present invention relates to line-type liquid ejecting heads, such as ink jet recording heads, and liquid ejecting apparatuses including the same. In particular, the invention relates to line-type liquid ejecting heads capable of stabilizing liquid supply to ejection units during droplet ejection operation, and liquid ejecting apparatuses including the same.
2. Related Art
Ink jet recording apparatuses, or printers, are categorized as liquid ejecting apparatuses. An ink jet recording apparatus includes, for example, an ink jet recording head (a liquid ejecting head called a serial head) that has a width smaller than the width of the recording medium, a head moving mechanism that reciprocates the recording head in a main scanning direction, and a transporting mechanism (recording medium feeding mechanism) that transports a recording medium, a target for liquid ejection such as recording paper, in a direction orthogonal to the main scanning direction for sub-scanning. The ink jet recording apparatus records images and the like on the recording medium by alternately repeating the main scanning of the recording head for ejecting ink droplets and the sub-scanning for transporting the recording medium. Such a method, however, has a problem in that, since the scanning speed of the recording head is limited, it takes a long time to record an image on the entirety of, for example, a relatively large recording medium.
Among apparatuses disclosed in recent years, an apparatus disclosed in FIGS. 2 to 4 of JP-A-6-183029 is configured to eject ink droplets from a long recording head immovably secured to an apparatus body. The recording head has nozzle openings aligned at a predetermined pitch with a width equivalent to the maximum recording width of the recording medium. Such a recording head is a line-type liquid ejecting head and is hereinafter referred to as a line head. This configuration does not require movement of the recording head in the main scanning direction and therefore enables recording of images and the like only by transportation of the recording medium in the sub-scanning direction. Accordingly, recording time is shorter than that of a configuration including the serial head.
A recording head of this type, such as the above-described line head, has groups of nozzles (rows of nozzles) provided for each type (color) of ink, and a common channel (reservoir) provided for each group of nozzles. Ink is supplied from an ink cartridge through a supply channel, such as an ink supply tube, to the common channel. The ink that has reached the common channel is distributed to the pressure chambers provided in correspondence with the nozzles. Driving of a pressure generator, such as a piezoelectric vibrator, generates a pressure change in the ink in the corresponding pressure chamber, whereby ink droplets are ejected through the nozzle openings.
Since this line head has more nozzle openings than the serial head, the common channel of the line head is naturally longer than that of the serial head in an arrangement direction of the rows of nozzles. This may cause a problem that the pressure chambers positioned farther from a connection between the common channel and the supply channel, through which ink is supplied from an ink source such as an ink cartridge to the common channel, have less ink supply. Particularly, in the case where ink droplets are to be ejected continuously at a higher frequency, ink supply may be delayed in the pressure chambers positioned farther from the connection.